Cancers, of which there are an estimated 200 different kinds, have the common property of uncontrolled growth of cells derived from normal tissues. More than 900,000 new cases of cancer are diagnosed annually in the United States and there are 600,000 deaths from cancer each year.
Despite considerable success in the treatment of several specific tumors, the overall survival rate for most cancers has not changed dramatically over the past few years. Surgery and combination chemotherapy have proved successful in the treatment of early localized disease but the development of clinical metastases, or spread of cancer to distal sites, remains the primary cause of cancer morbidity and mortality. Metastatic disease is incurable with a median survival of 2.2 years from the time of documented metastasis.
Metastasis describes the movement of cancer cells from one part of the body to the other causing spread of cancer to areas of the body apart from the primary growth. Metastasis is a dynamic process that involves a sequence of interrelated steps involving tumor cell adhesion to, and subsequent digestion, of basement membranes, intravasation into and survival in the vasculature, extravasation out of the vasculature at distant sites followed by growth in a distant organ environment.
Tumor invasion through tissue barriers and into lymph and blood vessels involves both mechanical and enzymatic processes. Tumors are known to contain and secrete various proteolytic enzymes such as urokinase plasminogen activator, metalloproteinases cathepsin-B, gelatinase, heparinase, and collagenase. Many malignant neoplasms produce higher levels of these proteolytic enzymes than benign tumors or corresponding normal tissues.
These enzymes have been shown to be active in most types of metastatic cancer including breast cancer; colon cancer, Reiter et al., The Role of Urokinase Receptor in Extracellular Matrix Degradation by HT29 Human Colon Carcinoma Cells, int. J. Cancer 53(3):444-50 (1993); epidermal carcinoma, Testa, "Loss of the Metastatic Phenotype by a Human Epidermoid Cell Line HEp-3 is Accompanied by Increased Expression of Tissue Inhibitor of Metalloproteinase 2, Cancer Res. 52(20):5597-603 (1992); lung adenocarcinoma, Hagiya et al, Urokinase-Type Plasminogen Activator and Its Specific Receptor in High Metastatic and Non Metastatic Cell Lines Derived From Human Lung Adenocarcinoma, Thromb. Res. 65(3):449-56, 1992; and cervical cancer, Sagimura-M et al, Clinical Significance of Urokinase-Type Plasminogen Activator in Invasive Cervical Cancer of the Uterus, Gynecol-Oncol 46(3):330-336 (1992). Invasion also involves an initial adhesion to the basement membrane and after enzyme digestion motility of the invasive cells occurs. The ideal anti-invasion agent would be one that inhibited one or more of these steps without significant toxicity.
Several different approaches to inhibiting invasion have been tried with limited success. The use of inhibitors of degradative enzymes that are involved in the invasive process is one approach that has been used often with varying degrees of success. Liotta, L. A., Steeg, P. S. and Stetler-Stevenson, W. G. Cancer Metastasis and Angiogenesis: An Imbalance of Positive and Negative Regulation. Cell, 64:327-336, 1991. This invention comprises a new strategy for inhibiting tumor invasion by inhibiting production of the proteolytic enzymes essential for tumor invasion and metastasis by use of phosphorothioate oligonucleotides.
Breast cancer remains a particularly significant metastatic disease due to its high prevalance. American women have a one in nine risk of developing breast cancer in their lifetime. The initial step in the proper treatment for breast cancer is the excisional biopsy followed by a definitive surgical procedure.
Unfortunately it has been shown that randomized patients of radical mastectomy versus simple mastectomy plus minus nodal radiation showed that surgery did not increase survival. Axillary nodal dissection was effective as a staging procedure but did not prolong survival. Regardless of the surgical procedure; patients failed systematically, i.e. bone, liver, lung, skin, brain metastatic lesions were found. Therefore, the treatment approach for breast cancer has undergone a dramatic evolution toward breast conservation procedures. Medial resection is followed by either adjuvant chemotherapy or endocrine therapy to eradicate micrometastasis reflecting the current approach that all invasive cancers be viewed as potentially metastatic to optimize survival.
A number of prognostic indicators have been helpful in identifying patients at risk for relapse. They include axillary lymph node involvement with tumor, tumor size, histopathological classification, histologic grade and nuclear grade, estrogen receptor, progesterone receptor, DNA ploidy and S-phase fraction. The presence of axillary lymph node involvement with tumor remains the strongest predictor of recurrence and survival. The relapse rate at 10 years increases direction proportionally with the number of axillary lymph node involvement with tumor ranging from 20% for patients without lymph node involvement with term to 60% for 1 to 3 lymph node to 85% for greater than 4 lymph noes involved with tumor. Tumor size is the second most important prognostic indicator.
Breast cancer is clearly a heterogeneous tumor at presentation. Unfortunately, currently available detection methods and prognostic indicators have major limitations, being unable to detect micrometastatic disease, or cells capable of early metastasis, or identify clones of cells with drug resistance.
Clearly a need exists in the art to inhibit metastasis, as a follow up to surgery or an initial treatment at diagnosis.
It is an object of the present invention to provide a method of inhibiting metastasis of cancer cells by treatment with antisense oligonucleotides.
It is another object of the invention to provide antisense phosphorothioate oligonucleotides complementary to the mRNA of protease enzymes involved in tumor invasion to block translation of these proteins.
Yet another object of the present invention is to provide antisense oligonucleotides which are nuclease resistant and non toxic.
Yet another object is to provide antisense oligonucleotides to urokinase plasminogen activator which inhibit metastasis in highly metastatic breast cancer cells.
Other objects of the invention will become apparent from the detailed description of the invention which follows.